SOMNAMBULISM (Latin for sleep-walking). Walking in sleep is the most palpable, but not the most marvelous characteristic of this condition. The person affected walks, rides, climbs, with the eyes shut or insensible; his movements are precise, cautious, leading him into positions of difficulty and peril, which, if perfectly alive to their real nature, or if acting under the influence of ordinary motives, he would avoid; and yet there appears to be a partial consciousness of surrounding objects, and an adaptation to circumstances.
Individuals have, while in this state, performed long journeys on foot or horseback, paying tolls, avoiding obstacles; they have successfully descended into coal-mines; they have ascended in safety to the roofs of houses, have climbed rocky cliffs, and successfully robbed eagles’ nests, during the night; millers, saddlers, grooms, seamstresses, have all performed their customary work with perfect exactitude, but without any recollection of their exertions or industry. Notwithstanding the accuracy with which many acts are performed, that particular senses may be dormant is proved by insensibility to loud noises, and by a cook eating cabbage which had been substituted for a salad which he had carefully and artistically prepared. The senses, in relation to the idea or train of ideas present to the mind, appear to be awake, and preternaturally acute. This fact has suggested the hypothesis, that certain faculties are wakeful, open to impressions, and actuated by volition; while others, and the mind in general, are plunged in profound sleep and unconsciousness.
This may be true, and is in harmony with the opinion, that the phenomena are an acted dream or delusion, and that what is seen, heard, or done, is the mere embodiment or repetition of former impressions or impulses, at the time before the mind. This may be illustrated by the case of the student narrated by the archbishop of Bordeaux, who composed a sermon and wrote out music while asleep; read them over, made corrections, scratched out lines, substituted others, put in its place a word that had been omitted, and continued to do all this, although a sheet of pasteboard was interposed between the writing and his face; showing that he was copying mental images, and not with the eye.
Somnambulism occurs in the sensitive and excitable, often in conjunction with other nervous affections, and is hereditary; so that it may be regarded as on, if not within, the boundary of disease.—Herbert Mayo, m.d., On the Truths contained in Popular Superstitions; Macnish, Philosophy of Sleep; Binns on Sleep.